#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<cstdio>
#include<algorithm>
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
const int maxn=2e5+1000;
typedef long long LL;
inline LL read(){LL x=0,f=1;char ch=getchar();	while (!isdigit(ch)){if (ch=='-') f=-1;ch=getchar();}while (isdigit(ch)){x=x*10+ch-48;ch=getchar();}
return x*f;}
vector<LL>g[maxn];
LL dep1[maxn],dep2[maxn];
void dfs1(LL u,LL fa){
    dep1[u]=dep1[fa]+1;
    for(LL i=0;i<g[u].size();i++){
        LL v=g[u][i];
        if(v==fa) continue;
        dfs1(v,u);
    }
}
void dfs2(LL u,LL fa){
    dep2[u]=dep2[fa]+1;
    for(LL i=0;i<g[u].size();i++){
        LL v=g[u][i];
        if(v==fa) continue;
        dfs2(v,u);
    }
}
int main(void)
{
  	cin.tie(0);std::ios::sync_with_stdio(false);
    LL n,x;cin>>n>>x;
    for(LL i=1;i<n;i++){
        LL u,v;cin>>u>>v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    dfs1(1,-1);
    dfs2(x,-1);
    LL ans=0;
    for(LL i=1;i<=n;i++){
        if(dep2[i]<dep1[i]){
            ans=max(ans,(dep1[i]-1)*2);
        }
    }
    cout<<ans<<"\n";
return 0;
}
